1. Field of the Invention
The present invention is generally related to a submersible object, such as a marine drive unit, and, more particularly, to a configuration of layers of an antifouling substance which is applied in two steps to provide an indicative arrangement of visually distinct appearances that facilitate the detection of missing portions of an outer layer.
2. Description of the Related Art
Those skilled in the art of marine propulsion systems are aware of many different methods for discouraging the growth of marine organisms on surfaces of boats, marine drives, and other submerged devices such as grates and pipes used to conduct the flow of liquids below the surface of a body of water. Some systems use electrically energized surfaces to induce the creation of chlorine bubbles in sea water applications or induce changes in the ionic characteristics of water near surfaces in fresh water applications. In addition, many different types of antifouling paints and chemical coatings have been used to discourage the growth of marine organisms, such as barnacles, on submerged surfaces. In addition, combinations of different colors have been used as visual indicators in various applications where the wear or degradation of an outer surface can be detected by comparing the color of the outer surface to a different color of an underlying surface.
U.S. Pat. No. 4,074,742, which issued to Chamblin on Feb. 21, 1978, describes an indicator for tire wear patterns. A multilayer adhesive strip is adhered to the tread of an automobile or other vehicle tire transversely of the tread and generally axially of the wheel. Each layer has a different color and wear on one part of the strip faster than another will expose a different color or colors that will indicate the wear pattern.
U.S. Pat. No. 5,303,574, which issued to Matossian et al. on Apr. 19, 1994, describes an evaluation of the extent of wear of articles. An article, such as a piece of manufacturing tooling, is modified prior to use by treating a portion of its surface to be worn so that the treated surface worn more than a preselected amount has a different appearance than the treated surface worn less than the preselected amount, using a treatment process in which the treated surface is at least as wear resistant as the untreated surface.
U.S. Pat. No. 5,403,390, which issued to Spera et al. on Apr. 4, 1995, describes a cuprous sulfide marine antifouling paint. The paint includes the ingredient of cuprous sulfide or cupric sulfide, both of which offer a hostile surface to chelating algae while retaining a repellant effect on barnacles and mollusks. The antifoulant coating results in a colorfast surface and the preferred embodiment has been devised to have a stable black color.
U.S. Pat. No. 5,468,532, which issued to Ho et al. on Nov. 21, 1995, describes a multilayer graphic article with color layer. The article comprises a substrate, at least one color layer disposed on the substrate, and a protective surface layer that overlies the substrate and the color layer. The color layer is visible through the surface layer and comprises a color agent in a copolymeric binder. The binder comprises the copolymerization product of an olefinic monomer and a second monomer having a pendant carboxyl group.
U.S. Pat. No. 5,603,161, which issued to Welsh on Feb. 18, 1997, describes a wear indicating shaving strip and blade assembly for a shaver. The indicator may incorporate a shaving aid, such that the visual wear indicator corresponds to releasing shaving agents, wear or oxidation of a cutting edge. The visual wear indicator may include a shaving aid composite which exhibits a first color to the user during an initial use and a different color during a subsequent use, wherein the transition from the first color to the second color is designed to correspond to a predetermined parameter of the shaver.
U.S. Pat. No. 5,697,329, which issued to Bell et al. on Dec. 16, 1997, describes a color coded safety belt or harness to indicate the age thereof. The harness is to be worn by a person to protect the person from a fall. The belt or harness is formed of first fibers of a predetermined first color and also includes at least one color coded indicator fiber woven therein to indicate the year of the manufacturer of the belt or harness.
U.S. Pat. No. 6,237,723, which issued to Salsman on May 29, 2001, describes a quick check brake indicator. A visual brake wear indicator gauge for a vehicle's disc brake system is described. A mounting bracket is fixed to the existing brake's caliper with a hollow housing extending from the bracket. The visual gauge has an indicator bar with straight length and a right angled indicator foot on one end that contacts an inside disc pad. This indicator bar extends through and within the gauge housing and is normally biased by a housing spring to contact the brake's disc pad.
U.S. Pat. No. 6,922,916, which issued to Potter on Aug. 2, 2005, describes footwear with outsole wear indicator. The wear indicator includes a plurality of strata that each have different properties, such as color. As portions of an individual stratum are worn away, corresponding portions of an underlying stratum are revealed. The underlying strata may be worn away in a similar manner to reveal further strata, thereby providing a wearer with the ability to determine the amount of wear that has occurred in an outsole.
U.S. Pat. No. 7,018,313, which issued to Nakamura on Mar. 28, 2006, describes a sprocket with wear limit indication. In a sprocket for use with a roller chain, a wear limit marker, having a different color from that of the base material of the sprocket, is provided on a side surface of a sprocket tooth adjacent to a keyway. The wear limit marker is disposed on an imaginary line extending in the direction of the pressure angle, and is located in a hole or groove provided in a side surface of the sprocket tooth. The marker makes it possible to determine easily and reliably whether or not wear at the location at which wear of a sprocket tooth proceeds most rapidly is within a predetermined limit, and the location of the marker makes it possible to evaluate wear conditions even when the sprocket is installed in a machine.
U.S. Pat. No. 7,341,777, which issued to Takahashi et al. on Mar. 11, 2008, describes a coating for inspection of cracking in a structure. The coating layer has dispersed therein microcapsules with a visualizing liquid sealed therein. It is formed on the surface of the structure and when a crack is developed in the structure and propagated to the coating layer, the microcapsules dispersed in the coating layer are ruptured and the visualizing liquid flows out from the ruptured microcapsules and reaches the surface of the coating layer along the crack in the coating layer. This makes it possible to detect the occurrence of the crack in the structure.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When a submersible object, such as a marine drive unit, is provided with an antifouling surface, two problems can occur. First, during manufacture, it is sometimes very difficult to determine whether or not the entire surface of the submersible object is properly coated with the antifouling substance. Secondly, after the submersible object is used, it is difficult to determine when the effectiveness of the antifouling surface has decreased sufficiently to require repair or recoating. It would therefore be significantly beneficial if an antifouling coating system could be provided in which, during manufacture, it is easy to tell whether or not the entire submersible surface of the object is adequately coated with the antifouling material and also make it possible, when in use, to determine if the submersible surface remains effectively coated with the antifouling material.